有氧运动改善自发性高血压大鼠肾纤维化的作用*

目的: 研究有氧运动训练对自发性高血压大鼠(SHR)肾脏纤维化影响, 探讨有氧运动对高血压肾损害的保护作用。方法: 8周龄雄性SHR和同龄Wistar京都大鼠(WKY)随机分为4组(n=6):安静WKY对照组(WKY-S)、安静SHR对照组(SHR-S)、低强度运动组(SHR-L)和中强度运动组(SHR-M)。SHR-L组、SHR-M组分别以14 m/min(最大有氧速度的35%)、20 m/min(最大有氧速度的50%)在0°坡度的运动跑步机上跑步,共运动14周,每周5次,每次60 min,WKY-S和SHR-S组安静饲养。14周后,运动训练结束72 h后检测大鼠血压;之后取血和肾脏检测血清肌酐SCr和尿素氮BUN含量,苏木精与伊红(HE)染色观察肾组织形态,Masson染色观察肾组织胶原沉积情况,计算肾脏胶原容积分数(CVF),检测肾脏 AngⅡ、AT1R、TGF-β、α-SMA、CTGF蛋白表达。结果: 与WKY-S组相比,SHR-S组的血压和血清SCr、BUN含量、肾脏CVF水平和AngⅡ、AT1R、TGF-β、α-SMA、CTGF蛋白表达均明显升高(P＜0.05);与SHR-S组相比,SHR-L组和SHR-M组血压和血清SCr、BUN含量、肾脏CVF水平和AngⅡ、AT1R、TGF-β、α-SMA、CTGF蛋白表达均明显下降(P＜0.05)且SHR-M组下降趋势更明显(P＜0.05)。结论: 有氧运动可通过抑制肾脏AngⅡ-AT1R-TGF-β通路,改善自发性高血压大鼠的肾纤维化与肾功能。     

Effects of aerobic and resistance exercise on cardiac remodelling and skeletal muscle oxidative stress of infarcted rats

We compared the influence of aerobic and resistance exercise on cardiac remodelling, physical capacity and skeletal muscle oxidative stress in rats with MI‐induced heart failure. Three months after MI induction, Wistar rats were divided into four groups: Sham; sedentary MI (S‐MI); aerobic exercised MI (A‐MI); and resistance exercised MI (R‐MI). Exercised rats trained three times a week for 12 weeks on a treadmill or ladder. Statistical analysis was performed by ANOVA or Kruskal‐Wallis test. Functional aerobic capacity was greater in A‐MI and strength gain higher in R‐MI. Echocardiographic parameters did not differ between infarct groups. Reactive oxygen species production, evaluated by fluorescence, was higher in S‐MI than Sham, and lipid hydroperoxide concentration was lower in A‐MI than the other groups. Glutathione peroxidase activity was higher in A‐MI than S‐MI and R‐MI. Superoxide dismutase was lower in S‐MI than Sham and R‐MI. Gastrocnemius cross‐sectional area, satellite cell activation and expression of the ubiquitin‐proteasome system proteins did not differ between groups. In conclusion, aerobic exercise and resistance exercise improve functional capacity and maximum load carrying, respectively, without changing cardiac remodelling in infarcted rats. In the gastrocnemius, infarction increases oxidative stress and changes antioxidant enzyme activities. Aerobic exercise reduces oxidative stress and attenuates superoxide dismutase and glutathione peroxidase changes.     

Diabetes influences cardiac extracellular matrix remodelling after myocardial infarction and subsequent development of cardiac dysfunction

This study was conducted to examine the influence of acute streptozotocin‐induced diabetes on cardiac remodelling and function in mice subjected to myocardial infarction (MI) by coronary artery ligation. Echocardiography analysis indicated that diabetes induced deleterious cardiac functional changes as demonstrated by the negative differences of ejection fraction, fractional shortening, stroke volume, cardiac output and left ventricular volume 24 hrs after MI. Temporal analysis for up to 2 weeks after MI showed higher mortality in diabetic animals because of cardiac wall rupture. To examine extracellular matrix remodelling, we used fluorescent molecular tomography to conduct temporal studies and observed that total matrix metalloproteinase (MMP) activity in hearts was higher in diabetic animals at 7 and 14 days after MI, which correlated well with the degree of collagen deposition in the infarct area visualized by scanning electron microscopy. Gene arrays indicated temporal changes in expression of distinct MMP isoforms after 1 or 2 weeks after MI, particularly in diabetic mice. Temporal changes in cardiac performance were observed, with a trend of exaggerated dysfunction in diabetic mice up to 14 days after MI. Decreased radial and longitudinal systolic and diastolic strain rates were observed over 14 days after MI, and there was a trend towards altered strain rates in diabetic mouse hearts with dyssynchronous wall motion clearly evident. This correlated with increased collagen deposition in remote areas of these infarcted hearts indicated by Masson's trichrome staining. In summary, temporal changes in extracellular matrix remodelling correlated with exaggerated cardiac dysfunction in diabetic mice after MI.     

Interleukin‐38 alleviates cardiac remodelling after myocardial infarction

Excessive immune‐mediated inflammatory reaction plays a deleterious role in ventricular remodelling after myocardial infarction (MI). Interleukin (IL)‐38 is a newly characterized cytokine of the IL‐1 family and has been reported to exert a protective effect in some autoimmune diseases. However, its role in cardiac remodelling post‐MI remains unknown. In this study, we found that the expression of IL‐38 was increased in infarcted heart after MI induced in C57BL/6 mice by permanent ligation of the left anterior descending artery. In addition, our data showed that ventricular remodelling after MI was significantly ameliorated after recombinant IL‐38 injection in mice. This amelioration was demonstrated by better cardiac function, restricted inflammatory response, attenuated myocardial injury and decreased myocardial fibrosis. Our results in vitro revealed that IL‐38 affects the phenotype of dendritic cells (DCs) and IL‐38 plus troponin I (TNI)‐treated tolerogenic DCs dampened adaptive immune response when co‐cultured with CD4⁺T cells. In conclusion, IL‐38 plays a protective effect in ventricular remodelling post‐MI, one possibility by influencing DCs to attenuate inflammatory response. Therefore, targeting IL‐38 may hold a new therapeutic potential in treating MI.     

Intramyocardial transplantation of cardiac telocytes decreases myocardial infarction and improves post‐infarcted cardiac function in rats

The midterm effects of cardiac telocytes (CTs) transplantation on myocardial infarction (MI) and the cellular mechanisms involved in the beneficial effects of CTs transplantation are not understood. In the present study, we have revealed that transplantation of CTs was able to significantly decrease the infarct size and improved cardiac function 14 weeks after MI. It has established that CT transplantation exerted a protective effect on the myocardium and this was maintained for at least 14 weeks. The cellular mechanism behind this beneficial effect on MI was partially attributed to increased cardiac angiogenesis, improved reconstruction of the CT network and decreased myocardial fibrosis. These combined effects decreased the infarct size, improved the reconstruction of the LV and enhanced myocardial function in MI. Our findings suggest that CTs could be considered as a potential cell source for therapeutic use to improve cardiac repair and function following MI, used either alone or in tandem with stem cells.     

Antihypertensive effect of low ethanol intake in spontaneously hypertensive rats

Light to moderate drinking in humans lowers the risk of coronary heart disease and may lower blood pressure. We examined the effect of chronic low daily alcohol consumption on blood pressure, platelet cytosolic free calcium [Ca²⁺]_i, tissue aldehyde conjugates and renal vascular changes in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). We also examined the effects of the same weekly amount of alcohol consumption over a one day period each week simulating weekend drinking in humans. Animals, age 7 weeks, were divided into six groups of six animals each and were treated as follows: WKY and SHR control, normal drinking water; WKY and SHR, 0.5% ethanol in drinking water; WKY and SHR, 3.5% ethanol in drinking water one day/week. After 14 weeks systolic blood pressure, platelet [Ca²⁺]_i, liver, kidney and aortic aldehyde conjugates were significantly higher (p < 0.05) in untreated SHRs as compared to untreated WKYs. Daily 0.5% ethanol consumption in SHRs significantly (p < 0.05) attenuated these changes and also attenuated smooth muscle cell hyperplasia and narrowing of the lumen in small arteries and arterioles of the kidney. WKY rats treated with 0.5% ethanol had lower aldehyde conjugates without any significant effect on blood pressure and platelet [Ca²⁺]_i as compared to WKY controls. Consumption of 3.5% ethanol one day/week did not affect blood pressure and associated changes in normotensive WKY rats or hypertensive SHRs as compared to their respective controls. These results suggest that chronic daily low ethanol intake lowers blood pressure in SHRs by lowering tissue aldehyde conjugates and cytosolic free calcium.     

Danqi soft capsule prevents infarct border zone remodelling and reduces susceptibility to ventricular arrhythmias in post‐myocardial infarction rats

Danqi soft capsule (DQ) is a traditional Chinese medicine containing Salvia miltiorrhiza and Panax notoginseng; it is safe and efficient in treating ischaemic heart diseases. The purpose of the present study was to assess whether DQ could prevent infarct border zone (IBZ) remodelling and decrease ventricular arrhythmias occurrence in post‐myocardial infarction (MI) stage. MI was induced by a ligation of the left anterior descending coronary artery. DQ was administered to the post‐MI rats started from 1 week after MI surgery for 4 weeks. The results showed that DQ treatment significantly attenuated tachyarrhythmia induction rates and arrhythmia score in post‐MI rats. In echocardiography, DQ improved left ventricular (LV) systolic and diastolic function. Histological assessment revealed that DQ significantly reduced fibrotic areas and myocyte areas, and increased connexin (Cx) 43 positive areas in IBZ. Western blot revealed that DQ treatment significantly reduced the protein expression levels of type I and III collagens, α‐smooth muscle actin (α‐SMA), transforming growth factor‐β1 (TGF‐β1) and Smad3 phosphorylation, while increasing Cx43 amounts. Overall, these findings mainly indicated that DQ intervention regulates interstitial fibrosis, Cx43 expression and myocyte hypertrophy by TGF‐β1/Smad3 pathway in IBZ, inhibits LV remodelling and reduces vulnerability to tachyarrhythmias after MI. This study presents a proof of concept for novel antiarrhythmic strategies in preventing IBZ remodelling, modifying the healed arrhythmogenic substrate and thus reducing susceptibility to ventricular arrhythmias in the late post‐MI period.     

Hydrogen gas inhalation ameliorates cardiac remodelling and fibrosis by regulating NLRP3 inflammasome in myocardial infarction rats

It is noteworthy that prolonged cardiac structural changes and excessive fibrosis caused by myocardial infarction (MI) seriously interfere with the treatment of heart failure in clinical practice. Currently, there are no effective and practical means of either prevention or treatment. Thus, novel therapeutic approaches are critical for the long-term quality of life of individuals with myocardial ischaemia. Herein, we aimed to explore the protective effect of H₂, a novel gas signal molecule with anti-oxidative stress and anti-inflammatory effects, on cardiac remodelling and fibrosis in MI rats, and to explore its possible mechanism. First, we successfully established MI model rats, which were then exposed to H₂ inhalation with 2% concentration for 28 days (3 hours/day). The results showed that hydrogen gas can significantly improve cardiac function and reduce the area of cardiac fibrosis. In vitro experiments further proved that H₂ can reduce the hypoxia-induced damage to cardiomyocytes and alleviate angiotensin II-induced migration and activation of cardiac fibroblasts. In conclusion, herein, we illustrated for the first time that inhalation of H₂ ameliorates myocardial infarction-induced cardiac remodelling and fibrosis in MI rats and exert its protective effect mainly through inhibiting NLRP3-mediated pyroptosis.     

The participation of brain NO synthase in blood pressure control of adult spontaneously hypertensive rats

Increased blood pressure (BP) in genetic hypertension is usually caused by high activity of sympathetic nervous system (SNS) which is enhanced by central angiotensin II but lowered by central nitric oxide (NO). We have therefore evaluated NO synthase (NOS) activity as well as neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS) protein expression in brainstem and midbrain of adult spontaneously hypertensive rats (SHR) characterized by enhanced sympathetic vasoconstriction. We also studied possible participation of brain NO in antihypertensive effects of chronic captopril treatment of adult SHR. NOS activity was increased in midbrain of SHR compared to Wistar-Kyoto (WKY) rats. This could be ascribed to enhanced iNOS expression, whereas nNOS expression was unchanged and eNOS expression was reduced in this brain region. In contrast, no significant changes of NOS activity were found in brainstem of SHR in which nNOS and iNOS expression was unchanged, but eNOS expression was increased. Chronic captopril administration lowered BP of adult SHR mainly by attenuation of sympathetic tone, whereas the reduction of angiotensin II-dependent vasoconstriction and the decrease of residual BP (amelioration of structural remodeling of resistance vessels) were less important. This treatment did not affect significantly either NOS activity or expression of any NOS isoform in the two brain regions. Our data do not support the hypothesis that altered brain NO formation contributes to sympathetic hyperactivity and high BP of adult SHR with established hypertension.     

Increased HO-1 expression and decreased iNOS expression in the hippocampus from adult spontaneously hypertensive rats

Brain expression of heme oxygenase (HO) and nitric oxide synthase (NOS) in hypertension may participate in the pathogenesis of hypertension-related neuronal disorders, such as vascular dementia. In the present study, expression levels of HO and NOS in spontaneously hypertensive rats (SHR) were investigated using Western immunoblotting assay. Expression level of inducible HO-1 in hippocampus of 4-wk prehypertensive SHR was about twofold of that in age-matched Sprague-Dawley (SD) rats (p<0.01). In 23-wk SHR with fully developed hypertension, hippocampal HO-1 level was significantly greater than that of age-matched SD rats (p<0.05), but not different from 4-wk SHR. There was no difference in expression levels of hippocampal HO-2 between SHR and SD rats at different ages. Total enzymatic activity of hippocampal HO was significantly greater in 23-wk SHR than in age-matched SD rats or 4-wk SD/SHR (p<0.01). Although hippocampal expression of nNOS protein was relatively unchanged, iNOS expression in 23-wk SHR was about fourfold lower than that in age-matched SD rats and 4-wk SD/SHR (p<0.01). Total enzymatic activity of hippocampal NOS was significantly lower in 23-wk SHR than in age-matched SD rats or 4-wk SD/SHR (p<0.01). Significantly suppressed Morris water maze performance was found in 23-wk SHR in comparison with age-matched SD rats. Because SHR has been used as a model of vascular dementia and hippocampus is essential for spatial learning and memory, understanding of altered HO/CO and NOS/NO systems in the hippocampus of adult SHR may shed light on the pathogenic development of memory deficits associated with vascular dementia.     

有氧运动对原发性高血压大鼠的降压作用及对骨骼肌VEGF、eNOS表达的影响

目的：了解运动训练对原发性高血压大鼠骨骼肌血管调节因子的影响,探讨运动降压的机制。方法：原发性高血压大鼠随机分为对照组（SHR-C）和训练组（SHR-T）,配对正常血压大鼠对照组（WKY-C）（n=7）。SHR-T进行10周游泳训练,每周训练5 d,每天运动1次,第1周每次运动40 min,第2周50 min,第3周增加到60 min后保持不变,直至训练完毕。SHR-T训练结束24 h后大鼠全部处死并提取比目鱼肌,RT-PCR和免疫印迹法测定血管内皮生长因子（VEGF）等指标。结果：与WKY-C比较,SHR-C骨骼肌VEGF、内皮型一氧化氮合酶（eNOS）蛋白明显低于对照组（P〈0.05）,训练前SHR-C、SHR-T两组血压显著性高于WKY-C（P〈0.01）;训练结束后,与SHR-C比较,SHR-T血压显著性降低（P〈0.05）,心率降低更加显著（P〈0.01）,VEGF mRNA及蛋白、VEGFR2、eNOS均显著性升高（P〈0.05）。结论：氧运动训练能明显降低高血压大鼠血压,促进骨骼肌VEGF mRNA和蛋白水平的表达,同步提高VEGFR2、eNOS蛋白含量,血管生长因子水平增加有利于血管生成并产生降压效应。     

Fatty acid composition of brain hemispheres of spontaneously hypertensive rats suckled by female Wistar rats

Total lipid fatty acid composition was investigated in brain hemispheres of male Spontaneously Hypertensive Rats (SHR), compared with normotensive Wistar Kyoto rats (WKY) used as controls. Both strains were suckled by adoptive Wistar mothers, and then fed a standard diet after weaning. No difference was observed between the two hemispheres of WKY killed either at 10 or 30 days. In SHR killed at 10 days, the two hemispheres showed differences, SHR left hemispheres exhibiting greater fatty acid composition changes than those of WKY, phenomenon that toned down at 30 days. Hence, SHR pups showed a different total lipid fatty acid composition of their brain hemispheres when compared with their WKY controls, though the two strains received the same diet. Genetically programmed hypertension might be, directly or not, involved in these changes.     

The CD4+AT2R+ T cell subpopulation improves post‐infarction remodelling and restores cardiac function

Myocardial infarction (MI) is a major condition causing heart failure (HF). After MI, the renin angiotensin system (RAS) and its signalling octapeptide angiotensin II (Ang II) interferes with cardiac injury/repair via the AT1 and AT2 receptors (AT1R, AT2R). Our study aimed at deciphering the mechanisms underlying the link between RAS and cellular components of the immune response relying on a rodent model of HF as well as HF patients. Flow cytometric analyses showed an increase in the expression of CD4⁺ AT2R⁺ cells in the rat heart and spleen post‐infarction, but a reduction in the peripheral blood. The latter was also observed in HF patients. The frequency of rat CD4⁺ AT2R⁺ T cells in circulating blood, post‐infarcted heart and spleen represented 3.8 ± 0.4%, 23.2 ± 2.7% and 22.6 ± 2.6% of the CD4⁺ cells. CD4⁺ AT2R⁺ T cells within blood CD4⁺ T cells were reduced from 2.6 ± 0.2% in healthy controls to 1.7 ± 0.4% in patients. Moreover, we characterized CD4⁺ AT2R⁺ T cells which expressed regulatory FoxP3, secreted interleukin‐10 and other inflammatory‐related cytokines. Furthermore, intramyocardial injection of MI‐induced splenic CD4⁺ AT2R⁺ T cells into recipient rats with MI led to reduced infarct size and improved cardiac performance. We defined CD4⁺ AT2R⁺ cells as a T cell subset improving heart function post‐MI corresponding with reduced infarction size in a rat MI‐model. Our results indicate CD4⁺ AT2R⁺ cells as a promising population for regenerative therapy, via myocardial transplantation, pharmacological AT2R activation or a combination thereof.     

自发性高血压大鼠心肌和血管组织牛磺酸的转运障碍

在自发性高血压大鼠（SHR）的心肌和主动脉血管组织上观察牛磺酸（taurine)转运和牛磺酸转运体（taurine transporter,TAUT) mRNA 的改变,结果显示,与对照组WKY大鼠相比,SHR组血浆牛磺酸水平和牛磺酸释放量增加,而心肌和血管组织牛磺酸水平和TAUT mRNA含量均降低,牛磺酸最大转运速率（Vmax)分别低24％和35％（P＜0．05）,米氏常数（Km)值分别高16％和39％（P＜0．05）,这些结果提示,SHR的心肌和血管组织牛磺酸转运障碍可能与TAUT活性和亲和力降低及TAUT基因水平的下调有关。     

Effect of chronic colchicine administration on the myocardium of the aging spontaneously hypertensive rat

Colchicine has been demonstrated to suppress the release of fibroblast growth factors, retard collagen formation and augment collagenase activity. Trials with colchicine in patients with hepatic fibrosis have suggested clinical benefit. The development of impaired myocardial function in the spontaneously hypertensive rat (SHR) is associated with a marked increase in myocardial fibrosis. The present study was carried out to test the hypothesis that chronic colchicine administration to the SHR would prevent the development of fibrosis and impaired myocardial performance.Colchicine (1 mg/l drinking water) was administered to male SHR and WKY rats from at age 13 months until 24 months or until evidence of heart failure was observed. Age-matched untreated SHR and colchicine treated and untreated WKY served as controls. At study, active and passive properties of isolated left ventricular muscle preparations were determined. Myocardial fibrosis was assessed by measuring hydroxyproline and histologic determination of interstitial cross-sectional area. Increases in LV hydroxyproline and interstitial area were found in untreated SHR relative to WKY; passive myocardial stiffness was increased and active muscle properties were depressed. In comparing colchicine treated vs untreated SHR, no differences in hydroxyproline, interstitial area or intrinsic myocardial function were found. In the WKY, colchicine increased myocardial interstitium and passive stiffness without changing hydroxyproline. Active myocardial function was not depressed.Thus, chronic colchicine administration neither attenuated the development of interstitial fibrosis nor prevented impaired myocardial function in the SHR. Colchicine treatment was associated with increased interstitium in WKY with increased passive myocardial stiffness. (Mol Cell Biochem 166: 45-54, 1997)     

Blood-brain barrier disruption in the hypothalamus of young adult spontaneously hypertensive rats

Vascular permeability and endothelial glycocalyx were examined in young adult spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP), and Wistar Kyoto rats (WKY) as a control, in order to determine earlier changes in the blood-brain barrier (BBB) in the hypothalamus in chronic hypertension. These rats were injected with horseradish peroxidase (HRP) as an indicator of vascular permeability. Brain slices were developed with a chromogen and further examined with cationized ferritin, a marker for evaluating glycocalyx. Staining for HRP was seen around vessels in the hypothalamus of SHR and SHRSP, but was scarce in WKY. The reaction product of HRP appeared in the abluminal pits of endothelial cells and within the basal lamina of arterioles, showing increased vascular permeability in the hypothalamus of SHR and SHRSP, whereas there were no leaky vessels in the frontal cortex of SHR and SHRSP, or in both areas of WKY. The number of cationized ferritin particles binding to the capillary endothelial cells was decreased in the hypothalamus of SHR and SHRSP, while the number decreased in the frontal cortex of SHRSP, compared with those in WKY. Cationized ferritin binding was preserved in some leaky arterioles, while it was scarce or disappeared in other leaky vessels. These findings suggest that BBB disruption occurs in the hypothalamus of 3-month-old SHR and SHRSP, and that endothelial glycocalyx is markedly damaged there without a close relationship to the early changes in the BBB.     

Transplantation of expanded bone marrow‐derived very small embryonic‐like stem cells (VSEL‐SCs) improves left ventricular function and remodelling after myocardial infarction

Adult bone marrow‐derived very small embryonic‐like stem cells (VSEL‐SCs) exhibit a Sca‐1⁺/Lin^–/CD45^– phenotype and can differentiate into various cell types, including cardiomyocytes and endothelial cells. We have previously reported that transplantation of a small number (1 × 10⁶) of freshly isolated, non‐expanded VSEL‐SCs into infarcted mouse hearts resulted in improved left ventricular (LV) function and anatomy. Clinical translation, however, will require large numbers of cells. Because the frequency of VSEL‐SCs in the marrow is very low, we examined whether VSEL‐SCs can be expanded in culture without loss of therapeutic efficacy. Mice underwent a 30 min. coronary occlusion followed by reperfusion and, 48 hrs later, received an intramyocardial injection of vehicle (group I, n= 11), 1 × 10⁵ enhanced green fluorescent protein (EGFP)‐labelled expanded untreated VSEL‐SCs (group II, n= 7), or 1 × 10⁵ EGFP‐labelled expanded VSEL‐SCs pre‐incubated in a cardiogenic medium (group III, n= 8). At 35 days after myocardial infarction (MI), mice treated with pre‐incubated VSEL‐SCs exhibited better global and regional LV systolic function and less LV hypertrophy compared with vehicle‐treated controls. In contrast, transplantation of expanded but untreated VSEL‐SCs did not produce appreciable reparative benefits. Scattered EGFP⁺ cells expressing α‐sarcomeric actin, platelet endothelial cell adhesion molecule (PECAM)‐1, or von Willebrand factor were present in VSEL‐SC‐treated mice, but their numbers were very small. No tumour formation was observed. We conclude that VSEL‐SCs expanded in culture retain the ability to alleviate LV dysfunction and remodelling after a reperfused MI provided that they are exposed to a combination of cardiomyogenic growth factors and cytokines prior to transplantation. Counter intuitively, the mechanism whereby such pre‐incubation confers therapeutic efficacy does not involve differentiation into new cardiac cells. These results support the potential therapeutic utility of VSEL‐SCs for cardiac repair.     

Engineering of TIMP‐3 as a LAP‐fusion protein for targeting to sites of inflammation

Tissue inhibitor of metalloproteinase (TIMP)‐3 is a natural inhibitor of a range of enzymes that degrade connective tissue and are involved in the pathogenesis of conditions such as arthritis and cancer. We describe here the engineering of TIMP‐3 using a novel drug‐delivery system known as the ‘LAP technology’. This involves creating therapeutic proteins in fusion with the latency‐associated peptide (LAP) from the cytokine TGF‐? to generate proteins that are biologically inactive until cleavage of the LAP to release the therapy. LAP‐TIMP‐3 was successfully expressed in mammalian cells and the presence of the LAP resulted in a 14‐fold increase in the quantity of recombinant TIMP‐3 produced. LAP‐TIMP‐3 was latent until release from the LAP by treatment with matrix metalloproteinase when it could inhibit proteases of the adamalysins and adamalysins with thrombospondin motifs families, but not matrix metalloproteinases, indicating that this version of TIMP‐3 is a more specific inhibitor than the native protein. There was sufficient protease activity in synovial fluid from human joints with osteoarthritis to release TIMP‐3 from the LAP fusion. These results demonstrate the potential for development of TIMP‐3 as a novel therapy for conditions where upregulation of catabolic enzymes are part of the pathology.